A major objective of these studies will be to further elucidate the differentiative pathways of human lymphoid cells under physiologic conditions and in individuals with leukemia-lymphoma. Emphasis will be on early stages of differentiation, especially in thymus and bone marrow. Cell surface antigens will be solubilized as previously using KCl and other methods; xenoantisera will be produced. Cell lines derived from individuals with leukemia will be used as 'monoclonal' sources of cells 'arrested' at early stages of differentiation within bone marrow or thymus. Recently detected thymocyte antigens will be pursued as will an antigen(s) found on a cell line (NALM-6-M1) of the pre-B (cytoplasmic Ig ion) phenotype. The presence or absence of the newly defined thymus and bone marrow (i.e., NALM-6) antigens will be studied on effector cells of the T cell (T suppressor, T helper) and B cell (cytoplasmic Ig ion, surface Ig ion, and secreted Ig ion) system. Xenoantisera will be utilized to evaluate the phenotypic characteristics of human leukemias and lymphomas. Evaluation of the heterogeneity of leukemias and lymphomas will continue.